I'm putting together (what I hope is a) definitive note on pile-up
in high energy hadron colliders, but another issue came up recently
that we should probably add to the table.

From the detector standpoint, it's not just the pile-up that's
important, but the *linear multiplicity density*.  For example,
we've been saying for the last three years that we would
level the luminosity in the HL-LHC with crab cavities.  Someone
finally noticed that while that lowers the total pile-up, it also shortens
the overlap region, so the linear density remains the same
and it's just as hard to distinguish individual interactions!
Now the plan is to use some other technique for leveling.

We should probably say something about the bunch length for
the detector simulation folks.  If this turns out to be important,
we could consider techniques to lengthen the bunches and
mitigate the effect.

Cheers,
Eric



On Mar 7, 2013, at 12:40 AM, Peskin, Michael E. wrote:

> Dear Colleagues,
> 
> Finally, everyone concerned has gotten back to me, and we are ready to post the
> "Official Energy Frontier Facilities List".  The purpose of this list is to insure that
> all studies of a given machine are done with the same energy and luminosity 
> assumptions, and that these assumptions are reasonable.  
> 
> You can find the list at:
> 
> http://www.snowmass2013.org/tiki-index.php?page=EF+Facilities+List
> 
> It is linked from the top Energy Frontier page.
> 
> I would be grateful if all of you, and especially the Technical Group, would look 
> at this list one more time before any errors in it become etched in stone. 
> 
> Chip and I strongly discourage the study of any machine option that is NOT 
> on this list.   If you have a case for adding another option, please let us know.
> 
> Thanks,
> 
> Michael 
> 
> 
> -------------------------------------------------------------------------------------------
>  Michael E. Peskin                           [log in to unmask]
>  HEP Theory Group, MS 81                       -------
>  SLAC National Accelerator Lab.        phone: 1-(650)-926-3250
>  2575 Sand Hill Road                       fax:     1-(650)-926-2525
>  Menlo Park, CA 94025 USA              www.slac.stanford.edu/~mpeskin/
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